diff --git a/src/Entity/MobileSession.php b/src/Entity/MobileSession.php
index f81578e2..70df5a81 100644
--- a/src/Entity/MobileSession.php
+++ b/src/Entity/MobileSession.php
@@ -44,7 +44,7 @@ class MobileSession
 
     // phone id
     /**
-     * @ORM\Column(type="string", length=50)
+     * @ORM\Column(type="string", length=50, nullable=true)
      */
     protected $phone_id;